Conversion of oxygenates to olefins

ABSTRACT

A process is described for converting an oxygenate-containing feedstock into one or more olefins in which the feedstock is contacted in a reaction zone with a fluidized bed of a particulate catalyst composition comprising a molecular sieve and at least one metal oxide having an uptake of carbon dioxide at 100° C. of at least 0.03 mg/m 2  of the metal oxide whereby at least part of the feedstock is converted into a product stream comprising one or more olefins and a carbonaceous material is deposited on the catalyst composition to produce a coked catalyst composition. The coked catalyst composition is separated from the product stream and divided into at least first and second portions. The first portion of the coked catalyst composition is contacted with a regeneration medium in a regeneration zone under conditions to remove at least part of the carbonaceous material from the coked catalyst composition and produce a regenerated catalyst composition, which is subsequently recycled to the reaction zone. The second portion of the coked catalyst composition is also recycled to the reaction zone but without being initially contacted with a regeneration medium.

FIELD

This invention relates to a method for catalytically converting a feedincluding an oxygenated hydrocarbon to a light olefin product in afluidized bed reactor system.

BACKGROUND

Light olefins, such as ethylene, propylene, butylenes and mixturesthereof, serve as feeds for the production of numerous importantchemicals and polymers. Typically, C₂–C₄ light olefins are produced bycracking petroleum refinery streams, such as C₃+ paraffinic feeds. Inview of limited supply of competitive petroleum feeds, production of lowcost light olefins from petroleum feeds are subject to waning supplylines. Efforts to develop light olefin production technologies based onalternative feeds have therefore increased.

An important type of alternative feed for the production of lightolefins is oxygenates, such as C₁–C₄ alkanols, especially methanol andethanol; C₂–C₄ dialkyl ethers, especially dimethyl ether (DME), methylethyl ether and diethyl ether; dimethyl carbonate and methyl formate,and mixtures thereof. Many of these oxygenates may be produced fromalternative sources by fermentation, or from synthesis gas derived fromnatural gas, petroleum liquids, carbonaceous materials, including coal,recycled plastics, municipal wastes, or any organic material. Because ofthe wide variety of sources, alcohol, alcohol derivatives, and otheroxygenates have promise as economical, non-petroleum sources for lightolefin production.

The preferred process for converting an oxygenate feedstock, such asmethanol, into one or more olefin(s), primarily ethylene and/orpropylene, involves contacting the feedstock with a molecular sievecatalyst composition. Molecular sieves are porous solids having pores ofdifferent sizes, such as zeolites or zeolite-type molecular sieves,carbons and oxides. The most commercially useful molecular sieves forthe petroleum and petrochemical industries are zeolites, for examplealuminosilicate molecular sieves. Zeolites in general have a one-, two-or three-dimensional crystalline pore structure having uniformly sizedpores of molecular dimensions that selectively adsorb molecules that canenter the pores, and exclude those molecules that are too large.

There are many different types of molecular sieve well known to converta feedstock, especially an oxygenate containing feedstock, into one ormore olefin(s). For example, U.S. Pat. No. 5,367,100 describes the useof the zeolite, ZSM-5, to convert methanol into olefin(s); U.S. Pat. No.4,062,905 discusses the conversion of methanol and other oxygenates toethylene and propylene using crystalline aluminosilicate zeolites, forexample Zeolite T, ZK5, erionite and chabazite; U.S. Pat. No. 4,079,095describes the use of ZSM-34 to convert methanol to hydrocarbon productssuch as ethylene and propylene; and U.S. Pat. No. 4,310,440 describesproducing light olefin(s) from an alcohol using a crystallinealuminophosphate, often designated AlPO₄.

Some of the most useful molecular sieves for converting methanol toolefin(s) are silicoaluminophosphate molecular sieves.Silicoaluminophosphate (SAPO) molecular sieves contain athree-dimensional microporous crystalline framework structure of [SiO₄],[AlO₄] and [PO₄] corner sharing tetrahedral units. SAPO synthesis isdescribed in U.S. Pat. No. 4,440,871, which is herein fully incorporatedby reference. SAPO molecular sieves are generally synthesized by thehydrothermal crystallization of a reaction mixture of silicon-,aluminum- and phosphorus-sources and at least one templating agent.Synthesis of a SAPO molecular sieve, its formulation into a SAPOcatalyst, and its use in converting a hydrocarbon feedstock intoolefin(s), particularly where the feedstock is methanol, are disclosedin U.S. Pat. Nos. 4,499,327, 4,677,242, 4,677,243, 4,873,390, 5,095,163,5,714,662 and 6,166,282, all of which are herein fully incorporated byreference.

Conversion of oxygenates to olefins generates and deposits carbonaceousmaterial (coke) on the molecular sieve catalysts used to catalyze theconversion process. Over-accumulation of these carbonaceous depositswill inhibit the catalyst's ability to promote the reaction. In order toavoid unwanted build-up of coke on the molecular sieve catalyst, theoxygenate to olefin process generally incorporates a second stepcomprising catalyst regeneration. During regeneration, the coke isremoved from the catalyst, typically by combustion with oxygen, which atleast partially restores the catalytic activity of the catalyst. Theregenerated catalyst then may be reused to catalyze the conversion ofoxygenates to olefins.

For example, SAPO-34 is known to be a selective molecular sieve catalystin the conversion of methanol to ethylene and propylene. However, itsexcellent selectivity to ethylene and propylene (maximum selectivityabout 40–43 wt % each) requires the formation of a carbon pool ascarbonaceous material is being deposited on the catalyst. With freshcatalyst, ethylene and propylene selectivities are about 20–24 wt % andabout 32–36 wt % respectively rising to their maximum values with timeas more carbonaceous material is being deposited. However, catalystactivity drops off rapidly when the carbonaceous material is greaterthan about 10 wt % (based on SAPO-34 molecular sieve content). Fixed bedoperation is not practical since catalyst life under a reasonable spacevelocity (at least 3 w/w/hr) is less than 2.5 hours. For this reasonmost current proposals for converting oxygenates to olefins employ afluidized bed reactor in which fine catalyst particles (typically of 10to 100 microns) are propelled through a riser reactor suspended in andthoroughly mixed with the oxygenate feed. The coked catalyst particlesare separated from the reactor effluent and then transferred to aregenerator where the coke is burned from the catalyst before thecatalyst is returned to the riser reactor.

However, fluidized bed reactor systems are capital intensive and itwould therefore be desirable to provide an improved molecular sievecatalyst composition and process which would enable smaller and cheaperreactor systems to be employed in conversion of oxygenates, such asmethanol, to olefins.

U.S. Pat. No. 4,873,390 to Lewis et al., incorporated herein byreference, teaches conversion of a feedstock, e.g., alcohols, to aproduct containing light olefins over a silicoaluminophosphate catalysthaving pores with a diameter of less than 5 Angstroms, wherein acarbonaceous deposit material is formed on the catalyst. The catalyst istreated to form a partially regenerated catalyst having from 2 to 30 wt.% of the carbonaceous deposit material. The catalyst may be employed ina fixed bed, ebullating bed, moving bed, a catalyst/liquid slurryreaction system or a fluidized bed reaction system, but is preferablyused in a fluidized state and is continuously transported between thereaction zone and the regeneration zone.

U.S. Pat. No. 6,023,005 to Lattner et al., incorporated herein byreference, discloses a method of producing ethylene and propylene bycatalytic conversion of oxygenate in a fluidized bed reaction processwhich utilizes catalyst regeneration. The process maintains desiredcarbonaceous deposits on the catalyst by removing only a portion of thetotal reaction volume of coked molecular sieve catalyst and regeneratingonly that portion of catalyst, which is then mixed back with theunregenerated remainder of catalyst. The resulting catalyst mixturecontains 2–30 wt % carbonaceous deposits.

U.S. Pat. No. 6,166,282 to Miller et al., incorporated herein byreference, discloses a fast-fluidized bed reactor for use in anoxygenate conversion process including an upper disengaging zone and alower reaction zone. The process is carried out in a reaction zonehaving a dense phase zone in the lower reaction zone and a transitionzone that extends into the disengaging zone. The feedstock in thepresence of a diluent is passed to the dense phase zone containing anon-zeolitic catalyst to effect at least a partial conversion to lightolefins and then passed to the transition zone above the dense phasezone to achieve essentially complete conversion. A portion of thecatalyst is withdrawn from above the transition zone in the disengagingzone, at least partially regenerated, and returned to a point above thedense phase zone, while catalyst is continuously circulated from thedisengaging zone to the lower reaction zone. The process includes afirst separation zone in the disengaging zone between the transitionzone and at least one cyclone separation stage to separate catalyst fromthe reaction product.

In our co-pending U.S. Patent Publication No. 10/364,156 published Sep.18, 2003, incorporated herein by reference, there is described acatalyst composition that exhibits enhanced lifetime when used in theconversion of oxygenates to olefins and which comprises a molecularsieve and at least one metal oxide having an uptake of carbon dioxide at100° C. of at least 0.03 mg/m² of the metal oxide. The metal oxide isselected from an oxide of Group 4 of the Periodic Table of Elements,either alone or in combination with an oxide selected from Group 2 ofthe Periodic Table of Elements and/or an oxide selected from Group 3 ofthe Periodic Table of Elements, including the Lanthanide series ofelements and the Actinide series of elements. The oxygenate conversionprocess is conveniently conducted as a fixed bed process, or moretypically as a fluidized bed process.

In our co-pending U.S. Patent Publication No. 10/364,870 published Sep.18, 2003, incorporated herein by reference, there is described acatalyst composition that exhibits enhanced lifetime when used in theconversion of oxygenates to olefins and which comprises a molecularsieve and at least one metal oxide having an uptake of carbon dioxide at100° C. of at least 0.03 mg/m² of the metal oxide. The metal oxide isselected from an oxide of a metal from Group 3 of the Periodic Table ofElements, the Lanthanide series of elements and the Actinide series ofelements. Again, the oxygenate conversion process is convenientlyconducted as a fixed bed process, or more typically as a fluidized bedprocess.

SUMMARY

The present invention relates to a process for converting anoxygenate-containing feedstock into one or more olefins, the processcomprising:

-   (a) contacting the feedstock in a reaction zone with a fluidized bed    of a particulate catalyst composition comprising a molecular sieve    and at least one metal oxide having an uptake of carbon dioxide at    100° C. of at least 0.03 mg/m² of the metal oxide whereby at least    part of the feedstock is converted into a product stream comprising    one or more olefins and a carbonaceous material is deposited on the    catalyst composition to produce a coked catalyst composition;-   (b) separating the coked catalyst composition from the product    stream;-   (c) contacting a first portion of the coked catalyst composition    with a regeneration medium in a regeneration zone under conditions    to remove at least part of the carbonaceous material from the coked    catalyst composition and produce a regenerated catalyst composition;-   (d) recycling at least part of the regenerated catalyst composition    to the reaction zone; and-   (e) passing a second portion of the coked catalyst composition to    the reaction zone without contacting said second portion of the    coked catalyst composition with a regeneration medium.

In one embodiment, the reaction zone comprises a riser and a mixture ofthe catalyst composition and the feedstock is passed upwardly throughthe riser during said contacting (a).

In another embodiment, the reaction zone comprises a dense or bubblingfluidized bed of the catalyst composition.

Conveniently, said second portion of the coked catalyst compositioncomprises between about 10% and about 99%, such as between about 20% andabout 97%, for example between about 50% and about 95%, of the totalcoked catalyst composition.

Conveniently, the metal of said at least one metal oxide is selectedfrom Group 2, Group 3 (including the Lanthanide and Actinide seriesmetals) and Group 4 of the Periodic Table of Elements using the IUPACformat described in the CRC Handbook of Chemistry and Physics, 78thEdition, CRC Press, Boca Raton, Fla. (1997). For example, the metaloxide may be selected from zirconium oxide, hafnium oxide, magnesiumoxide, calcium oxide, barium oxide, lanthanum oxide, yttrium oxide,scandium oxide, cerium oxide, and mixtures thereof.

Conveniently, the catalyst composition also includes at least one of abinder and a matrix material different from the metal oxide.

In one embodiment, the molecular sieve comprises a framework includingat least two tetrahedral units selected from [SiO₄], [AlO₄] and [PO₄]units, such as a silicoaluminophosphate.

In a preferred embodiment, the present invention employs a molecularsieve which has a pore diameter of less than 5.0 Angstroms, e.g., amolecular sieve having a framework-type selected from AEI, AFT, APC,ATN, ATT, ATV, AWW, BIK, CAS, CHA, CHI, DAC, DDR, EDI, ERI, GOO, KFI,LEV, LOV, LTA, MON, PAU, PHI, RHO, ROG, THO, and substituted formsthereof. For example, the molecular sieve may be selected from ALPO-18,ALPO-34, SAPO-17, SAPO-18, and SAPO-34.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph plotting methanol conversion against time on streamfor both a catalyst composition comprising SAPO-34 molecular sieve andyttria, and a catalyst composition comprising only of SAPO-34 molecularsieve.

FIG. 2 is a graph plotting coke selectivity against time on stream forboth a catalyst composition comprising SAPO-34 molecular sieve andyttria, and a catalyst composition comprising only of SAPO-34 molecularsieve.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Introduction

The present invention provides a continuous process for catalyticallyconverting an oxygenate-containing feedstock into one or more olefins ina reaction zone containing a fluidized bed of a particulate catalystcomposition in which part, but not all, of the coked catalystcomposition is passed to regeneration zone where coke is removed fromthe coked catalyst composition before it is recycled to the reactionzone. The remainder of the coked catalyst composition, after separationfrom the product stream, is recycled to the reaction zone withoutregeneration. In this way, there is a distribution in the level of cokeon the equilibrium catalyst; some catalyst particles may have beenrecycled many times without passage through the regenerator (and hencehave a coke level much higher than the average coke level of theequilibrium catalyst), whereas other catalyst particles may have maderepeated passages through the regenerator (and hence have a coke levelmuch lower than the average coke level of the equilibrium catalyst).

In the process of the invention, the catalyst composition employed inthe fluidized bed reaction zone comprises a molecular sieve and at leastone metal oxide having an uptake of carbon dioxide at 100° C. of atleast 0.03 mg/m² of the metal oxide. In particular, it has been foundthat combining a molecular sieve with such a metal oxide markedlydecreases the selectivity towards coke of the resulting catalystcomposition. Consequently, with each passage of the catalyst compositionthrough the reaction zone, a smaller amount of coke is deposited ontothe catalyst composition, resulting in lower activity losses. As aresult, the catalyst composition of the invention maintains a higheroverall level of activity as compared with a catalyst comprising themolecular sieve alone. In addition, smaller amounts of the catalystcomposition of the invention need to be passed to the regenerator tomaintain a given distributed coke level on the equilibrium catalyst. Asa result, using the catalyst composition of the invention allows thesize of the fluid bed reaction zone and/or the regenerator to be reducedwithout loss in overall methanol conversion and hence allows a reductionin capital investment.

Molecular Sieves

Molecular sieves have been classified by the Structure Commission of theInternational Zeolite Association according to the rules of the IUPACCommission on Zeolite Nomenclature. According to this classification,framework-type zeolite and zeolite-type molecular sieves, for which astructure has been established, are assigned a three letter code and aredescribed in the Atlas of Zeolite Framework Types, 5th edition,Elsevier, London, England (2001), which is herein fully incorporated byreference.

Crystalline molecular sieves all have a 3-dimensional, four-connectedframework structure of corner-sharing [TO₄] tetrahedra, where T is anytetrahedrally coordinated cation. Molecular sieves are typicallydescribed in terms of the size of the ring that defines a pore, wherethe size is based on the number of T atoms in the ring. Otherframework-type characteristics include the arrangement of rings thatform a cage, and when present, the dimension of channels, and the spacesbetween the cages. See van Bekkum, et al., Introduction to ZeoliteScience and Practice, Second Completely Revised and Expanded Edition,Volume 137, pages 1–67, Elsevier Science, B.V., Amsterdam, Netherlands(2001).

Non-limiting examples of molecular sieves are the small pore molecularsieves, AEI, AFT, APC, ATN, ATT, ATV, AWW, BIK, CAS, CHA, CHI, DAC, DDR,EDI ERI, GOO, KFI, LEV, LOV, LTA, MON, PAU, PHI, RHO, ROG, THO, andsubstituted forms thereof; the medium pore molecular sieves, AFO, AEL,EUO, HEU, FER, MEL, MFI, MTW, MTT, TON, and substituted forms thereof;and the large pore molecular sieves, EMT, FAU, and substituted formsthereof. Other molecular sieves include ANA, BEA, CFI, CLO, DON, GIS,LTL, MER, MOR, MWW and SOD. Non-limiting examples of preferred molecularsieves, particularly for converting an oxygenate containing feedstockinto olefin(s), include AEL, AFY, AEI, BEA, CHA, EDI, FAU, FER, GIS,LTA, LTL, MER, MFI, MOR, MTT, MWW, TAM and TON. In one preferredembodiment, the molecular sieve used in the present process has an AEItopology or a CHA topology, or a combination thereof, most preferably aCHA topology.

The small, medium and large pore molecular sieves have from a 4-ring toa 12-ring or greater framework-type. In a preferred embodiment, themolecular sieves have 8-, 10- or 12-ring structures and an average poresize in the range of from about 3 Å to 15 Å. In a more preferredembodiment, the molecular sieves, preferably silicoaluminophosphatemolecular sieves, have 8-rings and an average pore size less than about5 Å, such as in the range of from 3 Å to about 5 Å, for example from 3 Åto about 4.5 Å, and particularly from 3.5 Å to about 4.2 Å.

Molecular sieves have a molecular framework of one, preferably two ormore corner-sharing [TO₄] tetrahedral units, more preferably, two ormore [SiO₄], [AlO₄] and/or [PO₄] tetrahedral units, and most preferably[SiO₄], [AlO₄] and [PO₄] tetrahedral units. These silicon, aluminum, andphosphorus based molecular sieves and metal containing derivativesthereof have been described in detail in numerous publications includingfor example, R. Szostak, Handbook of Molecular Sieves, Van NostrandReinhold, New York, N.Y. (1992), which is herein fully incorporated byreference.

The more preferred molecular sieves include aluminophosphate (AlPO)molecular sieves and silicoaluminophosphate (SAPO) molecular sieves andsubstituted, preferably metal substituted, AlPO and SAPO molecularsieves. The most preferred molecular sieves are SAPO molecular sieves,and metal substituted SAPO molecular sieves. In an embodiment, the metalis an alkali metal of Group 1 of the Periodic Table of Elements, analkaline earth metal of Group 2 of the Periodic Table of Elements, arare earth metal of Group 3 of the Periodic Table of Elements, includingthe Lanthanides: lanthanum, cerium, praseodymium, neodymium, samarium,europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium,ytterbium and lutetium; and scandium or yttrium, a transition metal ofGroups 4 to 12 of the Periodic Table of Elements, or mixtures of any ofthese metal species. In one preferred embodiment, the metal is selectedfrom the group consisting of Co, Cr, Cu, Fe, Ga, Ge, Mg, Mn, Ni, Sn, Ti,Zn and Zr, and mixtures thereof. In another preferred embodiment, thesemetal atoms discussed above are inserted into the framework of amolecular sieve through a tetrahedral unit, such as [MeO₂], and carry anet charge depending on the valence state of the metal substituent. Forexample, in one embodiment, when the metal substituent has a valencestate of +2, +3, +4, +5, or +6, the net charge of the tetrahedral unitis between −2 and +2.

In one embodiment, the molecular sieve, as described in many of the U.S.Patents mentioned above, is represented by the empirical formula, on ananhydrous basis:mR:(M_(x)Al_(y)P_(z))O₂wherein R represents at least one templating agent, preferably anorganic templating agent; m is the number of moles of R per mole of(M_(x)Al_(y)P_(z))O₂ and has a value from 0 to 1, preferably 0 to 0.5,and most preferably from 0 to 0.3; x, y, and z represent the molefraction of Al, P and M as tetrahedral oxides, where M is a metalselected from one of Groups 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14 and Lanthanide's of the Periodic Table of Elements, preferably M isselected from one of the group consisting of Si, Co, Cr, Cu, Fe, Ga, Ge,Mg, Mn, Ni, Sn, Ti, Zn and Zr. In an embodiment, m is greater than orequal to 0.2, and x, y and z are greater than or equal to 0.01. Inanother embodiment, m is greater than 0.1 to about 1, x is greater than0 to about 0.25, y is in the range of from 0.4 to 0.5, and z is in therange of from 0.25 to 0.5, more preferably m is from 0.15 to 0.7, x isfrom 0.01 to 0.2, y is from 0.4 to 0.5, and z is from 0.3 to 0.5.

Non-limiting examples of SAPO and AlPO molecular sieves useful hereininclude one or a combination of SAPO-5, SAPO-8, SAPO-11, SAPO-16,SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34, SAPO-35, SAPO-36, SAPO-37,SAPO-40, SAPO-41, SAPO-42, SAPO-44 (U.S. Pat. No. 6,162,415), SAPO-47,SAPO-56, AlPO-5, AlPO-11, AlPO-18, AlPO-31, AlPO-34, AlPO-36, AlPO-37,AlPO-46, and metal containing molecular sieves thereof. Of these,particularly useful molecular sieves are one or a combination ofSAPO-18, SAPO-34, SAPO-35, SAPO-44, SAPO-56, AlPO-18 and AlPO-34 andmetal containing derivatives thereof, such as one or a combination ofSAPO-18, SAPO-34, AlPO-34 and AlPO-18, and metal containing derivativesthereof, and especially one or a combination of SAPO-34 and AlPO-18, andmetal containing derivatives thereof.

In an embodiment, the molecular sieve is an intergrowth material havingtwo or more distinct crystalline phases within one molecular sievecomposition. In particular, intergrowth molecular sieves are describedin the U.S. Patent Application Publication No. 2002/0165089 andInternational Publication No. WO 98/15496 published Apr. 16, 1998, bothof which are herein fully incorporated by reference. For example,SAPO-18, AlPO-18 and RUW-18 have an AEI framework-type, and SAPO-34 hasa CHA framework-type. Thus the molecular sieve used herein may compriseat least one intergrowth phase of AEI and CHA framework-types,especially where the ratio of CHA framework-type to AEI framework-type,as determined by the DIFFaX method disclosed in U.S. Patent ApplicationPublication No. 2002/0165089, is greater than 1:1.

The preferred molecular sieves useful herein for oxygenates to olefinsconversion are synthesized by techniques well-known to those skilled inthe art, as described in many of the references discussed above.

Metal Oxides

Metal oxides useful herein are those metal oxides, different fromtypical binders and/or matrix materials, that, when used in combinationwith a molecular sieve in a catalyst composition, are effective inextending of the useful life of the catalyst composition in theconversion of oxygenates to olefins. Quantification of the extension incatalyst life is determined by the Lifetime Enhancement Index (LEI) asdefined by the following equation:

${LEI} = \frac{\begin{matrix}{{Lifetime}\mspace{14mu}{of}\mspace{14mu}{Catalyst}\mspace{14mu}{in}} \\{{Combination}\mspace{14mu}{with}\mspace{14mu}{Active}\mspace{14mu}{Metal}\mspace{14mu}{Oxide}}\end{matrix}}{{Lifetime}\mspace{14mu}{of}\mspace{14mu}{Catalyst}}$where the lifetime of the catalyst or catalyst composition is thecumulative amount of oxygenate feedstock processed per gram of catalystcomposition until the conversion of the oxygenate feedstock by thecatalyst composition falls below some defined level, for example 10%. Aninactive metal oxide will have little to no effect on the lifetime ofthe catalyst composition, or will shorten the lifetime of the catalystcomposition, and will therefore have a LEI less than or equal to 1. Thusactive metal oxides of the invention are those metal oxides, differentfrom typical binders and/or matrix materials, that, when used incombination with a molecular sieve, provide a molecular sieve catalystcomposition that has a LEI greater than 1. By definition, a molecularsieve catalyst composition that has not been combined with an activemetal oxide will have a LEI equal to 1.0.

In particular, the metal oxides useful herein have an uptake of carbondioxide at 100° C. of at least 0.03 mg/m² of the metal oxide, such as atleast 0.035 mg/m² of the metal oxide. Although the upper limit on thecarbon dioxide uptake of the metal oxide is not critical, in general themetal oxides useful herein will have a carbon dioxide at 100° C. of lessthan 10 mg/m² of the metal oxide, such as less than 5 mg/m² of the metaloxide. Typically, the metal oxides useful herein have a carbon dioxideuptake of 0.04 to 0.2 mg/m² of the metal oxide.

In order to determine the carbon dioxide uptake of a metal oxide, thefollowing procedure is adopted. A sample of the metal oxide isdehydrated by heating the sample to about 200° C. to 500° C. in flowingair until a constant weight, the “dry weight”, is obtained. Thetemperature of the sample is then reduced to 100° C. and carbon dioxideis passed over the sample, either continuously or in pulses, again untilconstant weight is obtained. The increase in weight of the sample interms of mg/mg of the sample based on the dry weight of the sample isthe amount of adsorbed carbon dioxide.

In the Examples reported below, the carbon dioxide adsorption ismeasured using a Mettler TGA/SDTA 851 thermogravimetric analysis systemunder ambient pressure. The metal oxide sample is dehydrated in flowingair to about 500° C. for one hour. The temperature of the sample is thenreduced in flowing helium to 100° C. After the sample has equilibratedat the desired adsorption temperature in flowing helium, the sample issubjected to 20 separate pulses (about 12 seconds/pulse) of a gaseousmixture comprising 10 weight % carbon dioxide with the remainder beinghelium. After each pulse of the adsorbing gas the metal oxide sample isflushed with flowing helium for 3 minutes. The increase in weight of thesample in terms of mg/mg adsorbent based on the adsorbent weight aftertreatment at 500° C. is the amount of adsorbed carbon dioxide. Thesurface area of the sample is measured in accordance with the method ofBrunauer, Emmett, and Teller (BET) published as ASTM D 3663 to providethe carbon dioxide uptake in terms of mg carbon dioxide/m² of the metaloxide.

Suitable metal oxides include those metal oxides having a Group 4 metal,such as zirconium and/or hafnium, a Group 2 metal, such as magnesium,calcium, strontium and barium and/or a Group 3 metal (including theLanthanides and Actinides), such as yttrium, scandium, lanthanum, andcerium. In general, oxides of silicon, aluminum, and combinationsthereof are not preferred.

It is found that, by including an active metal oxide in combination witha molecular sieve, a catalyst composition can be produced having an LEIin the range of from greater than 1 to 2000, such as from about 1.5 toabout 1000. Typically catalyst compositions according to the inventionexhibit LEI values greater than 1.1, for example greater than 1.2, andmore particularly greater than 1.3, such as greater than 1.5, such asgreater than 1.7, such as greater than 2.

In one embodiment, the active metal oxide(s) has a BET surface area ofgreater than 10 m²/g, such as greater than 10 m²/g to about 300 m²/g. Inanother embodiment, the active metal oxide(s) has a BET surface areagreater than 20 m²/g, such as from 20 m²/g to 250 m²/g. In yet anotherembodiment, the active metal oxide(s) has a BET surface area greaterthan 25 m²/g, such as from 25 m²/g to about 200 m²/g. In a preferredembodiment, the active metal oxide(s) includes a yttrium oxide having aBET surface area greater than 20 m²/g, such as greater than 25 m²/g andparticularly greater than 30 m²/g.

In one embodiment, it is preferred to utilize a catalyst compositioncomprising at least two or more metal oxides, preferably selected fromoxides of Group 2, Group 3 (including Lanthanide and Actinide seriesmetals) and Group 4 metals. The metal oxides useful in the invention arecombinable in many ways to form the active mixed metal oxides. In anembodiment, the metal oxides are mixed together in a slurry or hydratedstate or in a substantially dry or dried state. Preferably the metaloxides are contacted in a hydrated state.

In a preferred embodiment, the active mixed metal oxides can beconsidered as having atomic level mixing of the Group 2, Group 3, and/orGroup 4 metals within the oxide, in which the atomic level mixing isachieved during synthesis of the mixed metal oxide.

The active metal oxide(s) used herein can be prepared using a variety ofmethods. It is preferable that the active metal oxide is made from ametal oxide precursor, preferably a Group 2 metal salt precursor, aGroup 3 metal salt precursor, and/or a Group 4 metal salt precursor.Other suitable sources of the metal oxides include compounds that formthese metal oxides during calcination, such as oxychlorides andnitrates. Alkoxides are also sources of the metal oxides, for examplezirconium n-propoxide.

In one embodiment, the active metal oxide(s) used herein ishydrothermally treated under conditions that include a temperature of atleast 80° C., preferably at least 100° C. The hydrothermal treatmenttypically takes place in a sealed vessel at greater than atmosphericpressure. However, a preferred mode of treatment involves the use of anopen vessel under reflux conditions. Agitation of the hydrated metaloxide in a liquid medium, for example, by the action of refluxing liquidand/or stirring, promotes the effective interaction of the hydratedoxide with the liquid medium. The duration of the contact of thehydrated oxide with the liquid medium is conveniently at least 1 hour,such as at least 8 hours. The liquid medium for this treatment typicallyhas a pH of about 6 or greater, such as 8 or greater. Non-limitingexamples of suitable liquid media include water, hydroxide solutions(including hydroxides of NH₄ ⁺, Na⁺, K⁺, Mg²⁺, and Ca²⁺), carbonate andbicarbonate solutions (including carbonates and bicarbonates of NH₄ ⁺,Na⁺, K⁺, Mg²⁺, and Ca²⁺), pyridine and its derivatives, andalkyl/hydroxylamines.

In one embodiment, where the active metal oxide(s) used herein consistsof two or more oxides selected from Groups 2, 3, and 4, the active mixedmetal oxide may be prepared by impregnation of a precursor to a secondoxide onto a preformed oxide. In an alternative embodiment, the firstformed oxide may be hydrothermally treated prior to impregnation. Forexample, a Group 3/Group 4 mixed metal oxide can be prepared byimpregnating a hydrothermally treated hydrated oxide of the Group 4metal with an aqueous solution containing an ion of the Group 3 metal,followed by drying. In a preferred embodiment, the Group 3 metal islanthanum or yttrium. The resulting material is then calcined,preferably in an oxidizing atmosphere, at a temperature of at leastabout 400° C., such as at least about 500° C., for example from about600° C. to about 900° C., and typically from about 650° C. to about 800°C. The calcination time may be up to 48 hours, such as for about 0.5 toabout 24 hours, for example for about 1 to about 10 hours. In apractical embodiment, calcination is carried out at about 700° C. forabout 1 to about 3 hours.

In yet another embodiment, where the active metal oxide(s) used hereinconsists of two or more oxides selected from Groups 2, 3, and 4, theactive mixed metal oxide may be prepared by combining a first liquidsolution comprising a source of at least one of the Group 2, 3, or 4metals with a second liquid solution comprising a source of an ion of atleast one other Group 2, 3, or 4 metal. This combination of twosolutions takes place under conditions sufficient to causeco-precipitation of a hydrated precursor to the mixed oxide material asa solid from the liquid medium. Alternatively, the sources of the allthe anions of the Group 2, 3, and/or 4 metal oxides may be combined in asingle solution. This solution may then be subjected to conditionssufficient to cause co-precipitation of the hydrated precursor to thesolid mixed oxide material, such as by the addition of a precipitatingreagent to the solution. For example, the precipitating agent(s)preferably is a base such as sodium hydroxide or ammonium hydroxide.Water is a preferred solvent for these solutions.

The temperature at which the liquid medium(s) is maintained during theco-precipitation is typically less than about 200° C., such as in therange of from about 0° C. to about 200° C. A particular range oftemperatures for co-precipitation is from about 20° C. to about 100° C.The resulting gel is preferably then hydrothermally treated attemperatures of at least about 80° C., such as at least about 100° C.The hydrothermal treatment typically takes place in a sealed vessel atgreater than atmospheric pressure. The gel, in one embodiment, ishydrothermally treated for up to about 10 days, such as up to about 5days, for example up to about 3 days.

The hydrated precursor to the metal oxide(s) is then recovered, forexample by filtration or centrifugation, and washed and dried. Theresulting material is preferably then calcined, typically in anoxidizing atmosphere, at a temperature of at least about 400° C., suchas at least about 500° C., for example from about 600° C. to about 900°C., and conveniently from about 650° C. to about 800° C., to form theactive metal oxide or active mixed metal oxide. The calcination time istypically up to 48 hours, such as for about 0.5 to 24 hours, for examplefor about 1.0 to 10 hours. In a practical embodiment, calcination iscarried out at about 700° C. for about 1 to about 3 hours.

Catalyst Compositions and Their Production

Catalyst compositions useful herein include any one of the molecularsieves previously described and one or more of the active metal oxidesdescribed above, optionally with a binder and/or matrix materialdifferent from the active metal oxide(s). Typically, the weight ratio ofthe molecular sieve to the active metal oxide(s) in the catalystcomposition is in the range of 1:10 to 100:1, such as from 1:5 to 75:1,particularly from 1:1 to 50:1, and more particularly from 2:1 to 40:1.

There are many different binders that are useful in forming the catalystcompositions used herein. Non-limiting examples of binders that areuseful alone or in combination include various types of hydratedalumina, silicas, and/or other inorganic oxide sols. One preferredalumina containing sol is aluminum chlorhydrol. The inorganic oxide solacts like glue binding the synthesized molecular sieves and othermaterials such as the matrix together, particularly after thermaltreatment. Upon heating, the inorganic oxide sol, preferably having alow viscosity, is converted into an inorganic oxide binder component.For example, an alumina sol will convert to an aluminum oxide binderfollowing heat treatment.

Aluminum chlorhydrol, a hydroxylated aluminum based sol containing achloride counter ion, has the general formula ofAl_(m)O_(n)(OH)_(o)Cl_(p).x(H₂O) wherein m is 1 to 20, n is 1 to 8, o is5 to 40, p is 2 to 15, and x is 0 to 30. In one embodiment, the binderis Al₁₃O₄(OH)₂₄Cl₇.12(H₂O) as is described in G. M. Wolterman, et al.,Stud. Surf. Sci. and Catal., 76, pages 105–144 (1993), which is hereinincorporated by reference. In another embodiment, one or more bindersare combined with one or more other non-limiting examples of aluminamaterials such as aluminum oxyhydroxide, γ-alumina, boehmite, diaspore,and transitional aluminas such as α-alumina, β-alumina, γ-alumina,δ-alumina, ε-alumina, κ-alumina, and ρ-alumina, aluminum trihydroxide,such as gibbsite, bayerite, nordstrandite, doyelite, and mixturesthereof.

In another embodiment, the binder is an alumina sol, predominantlycomprising aluminum oxide, optionally including some silicon. In yetanother embodiment, the binder is peptized alumina made by treating analumina hydrate, such as pseudobohemite, with an acid, preferably anacid that does not contain a halogen, to prepare a sol or aluminum ionsolution. Non-limiting examples of commercially available colloidalalumina sols include Nalco 8676 available from Nalco Chemical Co.,Naperville, Ill., and Nyacol AL20DW available from Nyacol NanoTechnologies, Inc., Ashland, Mass.

Where the catalyst composition contains a matrix material, this ispreferably different from the active metal oxide and any binder. Matrixmaterials are typically effective in reducing overall catalyst cost,acting as thermal sinks to assist in shielding heat from the catalystcomposition for example during regeneration, densifying the catalystcomposition, and increasing catalyst strength such as crush strength andattrition resistance.

Non-limiting examples of matrix materials include one or more non-activemetal oxides including beryllia, quartz, silica or sols, and mixturesthereof, for example silica-magnesia, silica-zirconia, silica-titania,silica-alumina and silica-alumina-thoria. In an embodiment, matrixmaterials are natural clays such as those from the families ofmontmorillonite and kaolin. These natural clays include subbentonitesand those kaolins known as, for example, Dixie, McNamee, Georgia andFlorida clays. Non-limiting examples of other matrix materials includehaloysite, kaolinite, dickite, nacrite, or anauxite. The matrixmaterial, such as a clay, may be subjected to well known modificationprocesses such as calcination and/or acid treatment and/or chemicaltreatment.

In a preferred embodiment, the matrix material is a clay or a clay-typecomposition, particularly a clay or clay-type composition having a lowiron or titania content, and most preferably the matrix material iskaolin. Kaolin has been found to form a pumpable, high solids contentslurry, to have a low fresh surface area, and to pack together easilydue to its platelet structure. A preferred average particle size of thematrix material, most preferably kaolin, is from about 0.1 μm to about0.6 μm with a D₉₀ particle size distribution of less than about 1 μm.

Where the catalyst composition contains a binder or matrix material, thecatalyst composition typically contains from about 1% to about 80%, suchas from about 5% to about 60%, and particularly from about 5% to about50%, by weight of the molecular sieve based on the total weight of thecatalyst composition.

Where the catalyst composition contains a binder and a matrix material,the weight ratio of the binder to the matrix material is typically from1:15 to 1:5, such as from 1:10 to 1:4, and particularly from 1:6 to 1:5.The amount of binder is typically from about 2% by weight to about 30%by weight, such as from about 5% by weight to about 20% by weight, andparticularly from about 7% by weight to about 15% by weight, based onthe total weight of the binder, the molecular sieve and matrix material.It has been found that a higher sieve content and lower matrix contentincreases the molecular sieve catalyst composition performance, whereasa lower sieve content and higher matrix content improves the attritionresistance of the composition.

The catalyst composition typically has a density in the range of from0.5 g/cc to 5 g/cc, such as from from 0.6 g/cc to 5 g/cc, for examplefrom 0.7 g/cc to 4 g/cc, particularly in the range of from 0.8 g/cc to 3g/cc.

In making the catalyst composition, the molecular sieve is first formedand is then physically mixed with the active metal oxide(s), preferablyin a substantially dry, dried, or calcined state. Most preferably themolecular sieve and active metal oxide(s) are physically mixed in theircalcined state. Without being bound by any particular theory, it isbelieved that intimate mixing of the molecular sieve and one or moreactive metal oxide(s) improves conversion processes using the molecularsieve composition and catalyst composition of the invention. Intimatemixing can be achieved by any method known in the art, such as mixingwith a mixer muller, drum mixer, ribbon/paddle blender, kneader, or thelike. Chemical reaction between the molecular sieve and the metaloxide(s) is unnecessary and, in general, is not preferred.

Where the catalyst composition contains a matrix and/or binder, themolecular sieve is conveniently initially formulated into a catalystprecursor with the matrix and/or binder and the active metal oxide isthen combined with the formulated precursor. The active metal oxide canbe added as unsupported particles or can be added in combination with asupport, such as a binder or matrix material. The resultant catalystcomposition can then be formed into useful shaped and sized particles bywell-known techniques such as spray drying, pelletizing, extrusion, andthe like. Typically, the catalyst particles used in the present processare generally spherical and have an average diameter of from about 40 μmto about 300 μm, such as from about 50 μm to about 250 μm, for examplefrom about 50 μm to about 200 μm, and conveniently from about 65 μm toabout 90 μm.

Once the molecular sieve catalyst composition is formed in asubstantially dry or dried state, to further harden and/or activate theformed catalyst composition, a heat treatment such as calcination, at anelevated temperature is usually performed. Typical calcinationtemperatures are in the range from about 400° C. to about 1,000° C.,such as from about 500° C. to about 800° C., such as from about 550° C.to about 700° C. Typical calcination environments are air (which mayinclude a small amount of water vapor), nitrogen, helium, flue gas(combustion product lean in oxygen), or any combination thereof.

In a preferred embodiment, the catalyst composition is heated in air ata temperature of from about 600° C. to about 700° C. Heating is carriedout for a period of time typically from 30 minutes to 15 hours, such asfrom 1 hour to about 10 hours, for example from about 1 hour to about 5hours, and particularly from about 2 hours to about 4 hours.

Oxygenate Conversion Process

The process of the invention is directed to the conversion of afeedstock containing one or more oxygenates to one or more olefin(s).Typically, the feedstock contains one or more aliphatic-containingoxygenate compounds such that the aliphatic moiety contains from 1 toabout 50 carbon atoms, such as from 1 to 20 carbon atoms, for examplefrom 1 to 10 carbon atoms, and particularly from 1 to 4 carbon atoms.Non-limiting examples of suitable oxygenate compounds include alcohols,including straight and branched chain aliphatic alcohols and theirunsaturated counterparts, such as methanol, ethanol, n-propanol andisopropanol; alkyl ethers such as dimethyl ether, diethyl ether,methylethyl ether and di-isopropyl ether; alkyl ketones such as dimethylketone; aldehydes such as formaldehydes, dimethylcarbonate and variousacids such as acetic acid.

In a preferred embodiment of the process of the invention, the feedstockis selected from one or more of methanol, ethanol, dimethyl ether,diethyl ether or a combination thereof, more preferably methanol anddimethyl ether, and most preferably methanol.

The various feedstocks discussed above are converted in the process ofthe invention primarily into one or more olefin(s). The olefin(s)produced from the feedstock typically have from 2 to 30 carbon atoms,preferably 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms,still more preferably 2 to 4 carbons atoms, and most preferably areethylene and/or propylene.

Using the catalyst composition of the invention for the conversion of afeedstock containing one or more oxygenates, the amount of olefin(s)produced based on the total weight of hydrocarbon produced is greaterthan 50 weight percent, typically greater than 60 weight percent, suchas greater than 70 weight percent, and preferably greater than 80 weightpercent. Moreover, the amount of ethylene and/or propylene producedbased on the total weight of hydrocarbon product produced is greaterthan 40 weight percent, typically greater than 50 weight percent, forexample greater than 65 weight percent, and preferably greater than 78weight percent. Typically, the amount ethylene produced in weightpercent based on the total weight of hydrocarbon product produced, isgreater than 20 weight percent, such as greater than 30 weight percent,for example greater than 35 weight percent. In addition, the amount ofpropylene produced in weight percent based on the total weight ofhydrocarbon product produced is typically greater than 20 weightpercent, such as greater than 25 weight percent, for example greaterthan 30 weight percent, and preferably greater than 35 weight percent.

In addition to the oxygenate component, such as methanol, the feedstockmay contain one or more diluent(s), which are generally non-reactive tothe feedstock or molecular sieve catalyst composition and are typicallyused to reduce the concentration of the feedstock. Non-limiting examplesof diluents include helium, argon, nitrogen, carbon monoxide, carbondioxide, water, essentially non-reactive paraffins (especially alkanessuch as methane, ethane, and propane), essentially non-reactive aromaticcompounds, and mixtures thereof. The most preferred diluents are waterand nitrogen, with water being particularly preferred.

The diluent(s), for example water, may be used either in a liquid or avapor form, or a combination thereof. The diluent(s) may be either addeddirectly to the feedstock entering a reactor or added directly to thereactor, or added with the molecular sieve catalyst composition.

The oxygenate conversion process of the invention is conducted bycontacting the oxygenate feedstock, together with any diluent(s), in areaction zone with a fluidized bed of the particulate catalystcomposition described above under conditions of temperature, pressureand space velocity such that the feedstock is converted into a productstream comprising one or more olefins and a carbonaceous material isdeposited on the catalyst composition to produce a coked catalystcomposition. The coked catalyst composition is then separated from theproduct stream and part of the coked catalyst composition is passed toregeneration zone where at least part of the coke is burnt off thecatalyst and the remainder of the coked catalysts is recycled to thereaction zone without regeneration. Typically the amount of the cokedcatalysts composition that is recycled to the reaction zone withoutregeneration is between about 10% and about 99%, such as between about20% and about 97%, for example between about 50% and about 95%, of thetotal coked catalyst composition.

The process can be conducted over a wide range of temperatures, such asin the range of from about 200° C. to about 1000° C., for example fromabout 250° C. to about 800° C., including from about 250° C. to about750° C., conveniently from about 300° C. to about 650° C., typicallyfrom about 350° C. to about 600° C. and particularly from about 350° C.to about 550° C.

Similarly, the process can be conducted over a wide range of pressuresincluding autogenous pressure. Typically the partial pressure of thefeedstock exclusive of any diluent therein employed in the process is inthe range of from about 0.1 kPaa to about 5 MPaa, such as from about 5kPaa to about 1 MPaa, and conveniently from about 20 kPaa to about 500kPaa.

The weight hourly space velocity (WHSV), defined as the total weight offeedstock excluding any diluents per hour per weight of molecular sievein the catalyst composition, typically ranges from about 1 hr⁻¹ to about5000 hr⁻¹, such as from about 2 hr⁻¹ to about 3000 hr⁻¹, for examplefrom about 5 hr⁻¹ to about 1500 hr⁻¹, and conveniently from about 10hr⁻¹ to about 1000 hr⁻¹. The superficial gas velocity (SGV) of thefeedstock including diluent(s) and reaction products within the reactionzone is typically at least 0.1 meter per second (m/sec), such as greaterthan 0.5 m/sec, such as greater than 1 m/sec, for example greater than 2m/sec, conveniently greater than 3 m/sec, and typically greater than 4m/sec. See for example U.S. Pat. No. 6,552,240.

The reaction zone may comprise a dense or bubbling fluidized bed of thecatalyst composition, although more preferably comprises a riser-typereaction zone in which a mixture of the catalyst composition and thefeedstock is passed upwardly through the riser. Suitable fluidized bedreaction systems are described in, for example, U.S. Pat. No. 4,076,796,U.S. Pat. No. 6,287,522 (dual riser), Fluidization Engineering, D. Kuniiand O. Levenspiel, Robert E. Krieger Publishing Company, New York, N.Y.1977, Riser Reactor, Fluidization and Fluid-Particle Systems, pages 48to 59, F. A. Zenz and D. F. Othmo, Reinhold Publishing Corporation, NewYork, 1960, U.S. Pat. No. 6,166,282 (fast-fluidized bed reactor), andU.S. patent application Ser. No. 09/564,613 filed May 4, 2000 (multipleriser reactor), which are all herein fully incorporated by reference.

Separation of the gaseous product stream generated in the reaction zonefrom the coked catalyst composition is conveniently effected in adisengaging zone connected to the reaction zone and provided withcyclone separators. Although cyclones are preferred, gravity effectswithin the disengaging vessel can also be used to separate the catalystcomposition from the gaseous effluent. Other methods for separating thecatalyst composition from the gaseous effluent include the use ofplates, caps, elbows, and the like. In one embodiment, the disengagingzone includes a stripping zone, typically in a lower portion thereof. Inthe stripping zone the coked catalyst composition is contacted with agas, preferably one or a combination of steam, methane, carbon dioxide,carbon monoxide, hydrogen, or an inert gas such as argon, preferablysteam, to recover adsorbed hydrocarbons from the coked catalystcomposition that is then introduced to the regeneration system.

The coked catalyst composition is withdrawn from the disengaging zoneand part, but not all, is introduced to a regeneration system. Theregeneration system comprises a regenerator where part of the cokedcatalyst composition is contacted with a regeneration medium underconditions of temperature, pressure and residence time sufficient toburn off at least part of the coke on the catalyst. Typical levels ofcoke on the regenerated portion of catalyst composition are in the rangeof from about 0.02 weight percent to about 2.0 weight percent, such asfrom about 0.02 weight percent to about 0.5 weight percent, based on theweight of the molecular sieve in the regenerated catalyst composition.

Non-limiting examples of suitable regeneration media include one or moreof oxygen, O₃, SO₃, N₂O, NO, NO₂, N₂O₅, air, air diluted with nitrogenor carbon dioxide, oxygen and water (U.S. Pat. No. 6,245,703), carbonmonoxide and/or hydrogen. Suitable regeneration conditions include atemperature in the range of from about 200° C. to about 1500° C., suchas from about 300° C. to about 1000° C., for example from about 450° C.to about 750° C., and conveniently from about 550° C. to 700° C. Theregeneration pressure may be in the range of from about 15 psia (103kPaa) to about 500 psia (3448 kPaa), such as from about 20 psia (138kPaa) to about 250 psia (1724 kPaa), including from about 25 psia (172kPaa) to about 150 psia (1034 kPaa), and conveniently from about 30 psia(207 kPaa) to about 60 psia (414 kPaa). The residence time of thecatalyst composition in the regenerator may be in the range of fromabout one minute to several hours, such as from about one minute to 100minutes.

The burning of coke in the regeneration step is an exothermic reaction,and in an embodiment, the temperature within the regeneration system iscontrolled by various techniques known in the art including feeding acooled gas to the regenerator vessel, operated either in a batch,continuous, or semi-continuous mode, or a combination thereof. Apreferred technique involves withdrawing the regenerated catalystcomposition from the regeneration system and passing it through acatalyst cooler to form a cooled regenerated catalyst composition. Thecatalyst cooler, in an embodiment, is a heat exchanger that is locatedeither internal or external to the regeneration system. Other methodsfor operating a regeneration system are disclosed in U.S. Pat. No.6,290,916 (controlling moisture), which is herein fully incorporated byreference.

The regenerated catalyst composition withdrawn from the regenerationsystem, preferably from a catalyst cooler, is combined with the portionof the coked catalyst which did not undergo regeneration, preferably ina storage vessel, and the mixture of regenerated and unregeneratedcatalyst is reccyed to the reaction zone.

The invention will now be more particularly described with reference tothe following Examples and the accompanying drawings.

EXAMPLE 1

Fifty grams of Y(NO₃)₃.6H₂O were dissolved with stirring in 500 ml ofdistilled water. The pH was adjusted to 9 by the addition ofconcentrated ammonium hydroxide. This slurry was then put inpolypropylene bottles and placed in a steambox (100° C.) for 72 hours.The product formed was recovered by filtration, washed with excesswater, and dried overnight at 85° C. A portion of this catalyst wascalcined to 600° C. in flowing air for 3 hours to produce yttrium oxide(Y₂O₃) having an uptake of carbon dioxide at 100° C. of 0.25 mg/m² ofthe metal oxide.

EXAMPLE 2

The following two catalyst compositions were prepared by mixing SAPO-34with the metal oxide of Example 1:

-   (a) 40 mg of SAPO-34/10 mg of metal oxide; and-   (b) 50 mg of SAPO-34 alone.

The resultant catalyst compositions were tested in a fixed bed reactorin the conversion of methanol at a temperature of 475° C., a pressure of25 psig (172.4 kPag) and a methanol weight hourly space velocity (WHSV)of 100 hr⁻¹. Both catalyst compositions were run for sufficient timesuch that the total cumulative amount of methanol converted per gram ofmolecular sieve was 11.5±0.3 g/g sieve. Following completion of eachrun, the amount of coke on each catalyst composition was determinedusing Temperature Programmed Oxidation. The methanol conversion as afunction of catalyst lifetime is shown in FIG. 1. From FIG. 1 it will beseen that the catalyst containing the metal oxide of Example 1 agedsignificantly more slowly than the SAPO-34 alone. FIG. 2 demonstratesthat the catalyst composition containing the metal oxide of Example 1had significantly reduced selectivity towards coke throughout thelifetime of the catalyst.

The total amount of coke for each catalyst composition at the end of therun is shown in Table 1.

TABLE 1 Catalyst Cumulative Methanol Coke on Catalyst CompositionConverted (g/g sieve) (wt. %) SAPO-34 11.36 16.50 SAPO-34 + Y₂O₃ 11.794.92

The data of Table 1 shows that the amount of coke on the catalyst afteran equivalent amount of methanol has been converted is significantlyless for the catalyst containing the metal oxide of Example 1 than forthe SAPO-34 alone. This implies that using the catalyst composition ofthis invention results in more of the methanol fed to the reaction zonebeing converted into useful products. In addition, the lower amount ofcoke deposited on the catalyst reduces the amount of catalyst that needsto be regenerated to maintain a desired distributed coke level on theequilibrium catalyst.

If used in a fluidized bed reactor system, the enhanced activity andreduced coke selectivity of the metal oxide-containing catalystcomposition would enable a reduction in the size of the reactor and/orregenerator required to provide a given methanol utilization.

While the present invention has been described and illustrated byreference to particular embodiments, those of ordinary skill in the artwill appreciate that the invention lends itself to variations notnecessarily illustrated herein. For this reason, reference should bemade solely to the appended claims for purposes of determining the truescope of the present invention.

1. A process for converting an oxygenate-containing feedstock into oneor more olefins, the process comprising: (a) contacting the feedstock ina reaction zone with a fluidized bed of a particulate catalystcomposition comprising a molecular sieve and at least one metal oxide,selected from Group 3 metals. Lanthanide series metals, Actinide seriesmetals, and Group 4 metals of the Periodic Table of Elements, having anuptake of carbon dioxide at 100° C. of at least 0.03 mg/m² of the metaloxide whereby at least part of the feedstock is converted into a productstream comprising one or more olefins and a carbonaceous material isdeposited on the catalyst composition to produce a coked catalystcomposition; (b) separating the coked catalyst composition from theproduct stream; (c) contacting a first portion of the coked catalystcomposition with a regeneration medium in a regeneration zone underconditions to remove at least part of the carbonaceous material from thecoked catalyst composition and produce a regenerated catalystcomposition; (d) recycling at least part of the regenerated catalystcomposition to the reaction zone; and (e) passing a second portion ofthe coked catalyst composition to the reaction zone without contactingsaid second portion of the coked catalyst composition with aregeneration medium.
 2. The process of claim 1 wherein the reaction zonecomprises a riser and a mixture of the catalyst composition and thefeedstock is passed upwardly through the riser during said contacting(a).
 3. The process of claim 1 wherein reaction zone comprises a denseor bubbling fluidized bed of the catalyst composition.
 4. The process ofclaim 1 wherein said second portion of the coked catalyst compositioncomprises between about 10% and about 99% of the total coked catalystcomposition.
 5. The process of claim 1 wherein said second portion ofthe coked catalyst composition comprises between about 20% and about 97%of the total coked catalyst composition.
 6. The process of claim 1wherein said second portion of the coked catalyst composition comprisesbetween about 50% and about 95% of the total coked catalyst composition.7. The process of claim 1 wherein said the amount of carbonaceousmaterial on the regenerated catalyst composition is in the range of fromabout 0.02 weight percent to about 2.0 weight percent, based on theweight of the molecular sieve in the regenerated catalyst composition.8. The process of claim 1 wherein said the amount of carbonaceousmaterial on the regenerated catalyst composition is in the range of fromabout 0.02 weight percent to about 0.5 weight percent, based on theweight of the molecular sieve in the regenerated catalyst composition.9. The process of claim 1 wherein the oxygenate-containing feedstockcomprises methanol, ethanol, dimethyl ether, diethyl ether or acombination thereof.
 10. The process of claim 1 wherein the contactingconditions in (c) include a temperature of about 200° C. to about 1000°C., a pressure of about 0.1 kPaa to about 5 Mpaa and a weight hourlyspace velocity (WHSV) of about 0.1 hr⁻¹ to about 500 hr⁻¹.
 11. Theprocess of claim 1 wherein the contacting conditions in (d) include atemperature of about 200° C. to about 1500° C. and a pressure of about15 psia (103 kPaa) to about 500 psia (3448 kPaa).
 12. The process ofclaim 1 wherein said metal oxide has an uptake of carbon dioxide at 100°C. of at least 0.035 mg/m² of the metal oxide.
 13. The process of claim1 wherein said metal oxide has an uptake of carbon dioxide at 100° C. ofabout 0.04 to about 5 m/m² of the metal oxide.
 14. The process of claim1 wherein said metal oxide has a surface area greater than 10 m²/g. 15.The process of claim 1 wherein said catalyst composition also includesat least one of a binder and a matrix material different from said metaloxide.
 16. The process of claim 1 wherein said catalyst composition alsoincludes a binder and a matrix material each being different from oneanother and from said metal oxide.
 17. The process of claim 6 whereinthe binder is an alumina sol and the matrix material is a clay.
 18. Theprocess of claim 1 wherein said at least one metal oxide is selectedfrom zirconium oxide, oxide, yttrium oxide, scandium oxide, ceriumoxide, and mixtures thereof.
 19. The process of claim 1 wherein theweight ratio of the molecular sieve to metal oxide is in the range offrom 1:10 to 100:1.
 20. The process of claim 1 wherein the molecularsieve has a pore diameter less than 6 Angstrom.
 21. The process of claim1 wherein the molecular sieve comprises a framework including at leasttwo tetrahedral units selected from [SiO₄], [AlO₄] and [PO₄] units. 22.The process of claim 21 wherein the molecular sieve comprises asilicoaluminophosphate.
 23. The process of claim 21 wherein themolecular sieve comprises a CHA framework-type molecular sieve.
 24. Theprocess of claim 21 wherein the molecular sieve further comprises an AEIframework-type molecular sieve.